ИСТИНА

Large settlements on permafrost have a significant impact on the natural geological conditions. The first feature that affects development on permafrost is soil temperature change, which defines the bearing capacity of frozen foundations and therefore the stability of engineering facilities. Temperature regime depends on both climatic trends and anthropogenic effects, their duration, intensity and the area of impact. Permafrost degradation within built-up areas is typical not only for Norilsk region, but also for many other large settlements in the Russian Arctic. Uunlike the other cities where temperature rising generally driven by climate change (e. g. Salekhard, Chita, etc.), Norilsk has made the most significant contribution to the development and use of the territory. We analyzed the temperature measured in boreholes within microdistricts of the city with different permafrost conditions. Measurement periods ranged from 2 to 70 years. We built temperature curves and profiles of soils under buildings for different periods of time, which shows the examples of both temporal and spatial changes. Three main trends in soil temperature regime were revealed: a decrease in temperature, growth and invariability. The most typical was the most dangerous trend – a serious warming of soils foundation (almost 45% of all buildings). Since the majority of the buildings in Norilsk built on pile foundations, which bearing capacity is provided by freezing of piles with frozen ground, the increase in temperature leads to a reduction in bearing capacity and, often, to the failure of the base. The reasons are climate warming trends as well as disturbances during buildings construction and exploitation. However, the leading reason is violation of cold ventilated cellars use (engineering solutions of maintaining of a low substrate temperature): flooding from the unregulated sewage, littering and obstruction of ventilation. This trend observed at bases of both old and modern buildings. At the same time, the facilities with a tendency to a lowering of soil temperature also occupy a significant proportion of the city total area. This trend provided by correct constructions exploitation as well as installation of heat pipe termosyphones, which compensates climate-warming trend. The temperature stability observed frequently that underlines the dynamical response of permafrost to external interference. The dynamics of temperature regime creates a mosaic and inhomogeneous structure of permafrost conditions, which undoubtedly complicates the ongoing development of the Norilsk area. The studies of temperature changes reasons help to find solutions to the buildings deformability problems and structures associated with the loss of bearing capacity and potentially facilitate the development of the permafrost zone.